When you visit Craigslist, you’re instantly redirected to a highly specific, regional site. But what exactly is this region? Just what do these purely digital boundaries look like?

Click to zoom.

The United Zip Codes of Craigslist is a fascinating marriage of the borders of Craigslist’s regional pages and our own zip code system. It’s by information visualization company IDV, who deployed a Voronoi algorithm to draw Craigslist’s regional zones with approximated boundaries. Once they built that basic map of Craigslist coverage, they combined it with U.S. zip code information.

So what you’re actually looking at is every zip code within any given Craigslist zone smashed into a glob. Or, put differently, you’re looking at the U.S. zip code system if reorganized with Craigslist logic–and given that Craigslist logic is roughly based on the regions people consider close-ish to home, it’s a lot more useful than your typical city or state dividers in discerning where our true boundaries lie.

“Whenever we can use real-world data to enhance or maybe even replace standard notions of political geographic boundaries, it’s an interesting opportunity,” says IDV’s John Nelson. “These Craigsmaps are examples of that, and the zip code reference associated with them is a sort of compromise. We want a practical look at a phenomenon but having a reference of zip codes makes these shapes immediately actionable to more folks.”

To, say, a specific marketer, IDV’s map of Craigslist zip code associations (that comes with a complete list of included zip codes, should you want to dig through it), could be very useful. But to you and me? It’s a fun three minutes as you discover that Maine only has one Craigslist site and store that tidbit away for future cocktail conversation.MW